A typical syringe includes a body defining a cylindrical or barrel shape, a manually-engageable plunger slidably received within the body, an outlet for dispensing fluid pushed or compressed by the plunger therethrough, and a luer type fitting at the outlet of the body. A luer type fitting, such as sold under the trademark LUER-LOK®, is connectable to another luer fitting on a needle, for example, to form a luer connection between the needle and body. Typically, the needle defines a female luer fitting and the syringe body defines a male luer fitting that is receivable within the female luer fitting to form a leak-free connection between the needle and syringe body.
The luer taper is a standardized system of small-scale fluid fittings used for making leak-free connections between a male-taper fitting and its mating female part on medical and laboratory instruments, including hypodermic syringe tips, needles and stopcocks. Luer_locking fittings are securely joined by means of a tabbed hub on the female fitting which screws into threads in a sleeve on the male fitting. Luer-slip fittings conform to luer taper dimensions and are pressed together and held by friction without any threads. Luer components are manufactured either from metal or plastic and are available from many companies worldwide.
One of the drawbacks of known syringes is that they are not as effective as desired for dispensing multiple doses of substances, such as medicaments, pharmaceuticals, vaccines, liquid nutrition products, supplements, or other products. A typical prior art syringe is prefilled with a unit dose, and therefore it can be used once on a single patient. Other syringes that are not prefilled have significant drawbacks if used to dispense multiple doses. Dosage metering can be inaccurate and difficult to control. The substance in the body of the syringe to be dispensed is in open fluid communication through the outlet port with the luer connection and/or the needle connected thereto. Any germs, bacteria, or other contaminants at the needle or luer connection, for example, can travel into the body of the syringe and contaminate the remaining substance stored therein. Thus, although a luer connection allows a needle to be discarded after single patient use and replaced with a fresh needle, the substance in the syringe body nevertheless can become contaminated during or between dispensing multiple doses. This, in turn, can lead to the spread of germs, bacteria or other contaminants from one patient to another and give rise to harmful results.